Implants for the aforementioned purpose are known, e.g. from U.S. Pat. Nos. 4,180,910, 4,447,209 and from the book Oral Implantology [Orale Implantologie], Andre Schroeder, Franz Sutter and Gisbert Krekeler, Georg Thieme Verlag [publisher], Stuttgart, New York, 1988, title page and pages 66-71, 118-151, 178-187, 202-217, 228-243. These implants comprise a base or anchor comprising at least one hollow cylindrical part, which base is intended for insertion in a jaw bone. In order to anchor an implant in a jaw bone, the latter is provided with a hole for the hollow cylindrical part of the base or for each hollow cylindrical part of the base, respectively. Depending on the type and dimensioning of the implant, this hole can comprise e.g. an outer portion formed by means of a full bore hole, i.e. one which is hollow across its entire diameter, and a base or inner portion formed by means of an annular groove or kerf or can consist exclusively of a full bore hole or can consist exclusively of an annular groove and can possibly also be provided with an internal thread. In the aforementioned book, tools are also disclosed for producing holes in jaw bones. Heating above a maximum temperature of approximately 45.degree. C. to 47.degree. C. should be avoided in order that the bone material adjoining the holes does not die when producing the holes. As is likewise mentioned in the aforementioned book, the tools can be cooled with a liquid coolant, e.g. an aqueous, sterile, normal saline solution or Ringer's solution, which can be supplied e.g. to the outside of the tools, according to the book, in order to prevent excessive heating.
A device known from DE-C-3 433 570 comprises a rotatable tool with two pieces which can be screwed together so as to be detachable. One of these pieces forms a cutting part as well as a shoulder provided with an internal thread, and the other piece forms the shaft or--more precisely--at least its main part. The piece of the tool forming the main part of the shaft comprises an external thread, which is screwed together with the aforementioned internal thread, a collar and an annular groove on its side remote of the cutting part. The tool comprises a passage which makes it possible for it to be cooled on the inside with a liquid coolant. This passage comprises an axial hole, which extends from the front side at the free end of the cutting part at least until the annular groove, and a radial bore hole connecting the axial hole with the annular groove. A sleeve, which serves to feed the coolant to the tool and encloses the shaft in the area of the annular groove, is held so as to be rotatable and axially displaceable between the collar of the shaft and a separate adjusting ring fastened at the shaft. The sleeve is sealed with a sealing ring against the collar and the adjusting ring in each instance, and, together with the annular groove of the shaft, defines an annular duct and is provided with a coolant inlet opening into the latter.
Since the screwed-together threads of the two pieces of the tool must have a certain minimum length and since the adjusting ring also has a certain axial dimensioning, the tool is necessarily comparatively long and, in particular, longer than a tool comprising an identical cutting part constructed in a conventional manner, i.e. without inner cooling. The comparatively long length of the tool known from DE-C-3 433 570 impedes the dental treatment which is effected by means of the tool, particularly the treatment effected in the area of the molars. DE-C-3 433 570 contains no description as to how the adjusting ring is fastened. In commercially known devices constructed in general according to this publication, the adjusting ring is pressed on to the shaft, i.e. by means of a press-fit connection, so that it is not possible in practice for a dentist or his assistant to remove the sleeve from the shaft and mount it again on the latter. The tool and the sleeve must therefore be cleaned and sterilized in the assembled state before using, which makes it difficult to clean and sterilize satisfactorily. In addition, the device is comparatively expensive to manufacture because of the great number of parts to be produced and connected with one another.